1. Field of the Invention
This invention relates to a liquid treatment apparatus or system wherein a liquid treatment media bed is regenerated with a solution formed by dissolving a solid material in a liquid. More particularly, it relates to apparatus for monitoring the amount of solid material available for forming the solution.
2. Background of the Invention
Some liquid treatment systems have a liquid treatment medium bed which is regenerated by passing a solution formed by dissolving a solid in a liquid through the bed. In the use of such systems, it is desirable to make those persons responsible for proper operation of the system aware of the need to replenish the solid material before it is totally exhausted. Liquid treatment system having a control system which provides for automatic regeneration of a liquid treatment medium, may initiate a regeneration cycle even though the solid, which is dissolved to form the regenerant solution, has been exhausted. The solid material having been exhausted, the flow of untreated liquid during the several cycles of a regeneration will cause even further depletion of the liquid treatment medium bed.
One of the most common liquid treatment systems of this type is the domestic water softener which removes hardness from raw water by passing it through a tank containing a liquid treatment medium bed, typically formed of resin beads. A salt solution, that is brine, is passed through the resin bed to restore its softening capacity. The brine is formed in a container which is connected by a liquid flow passage to the tank containing the resin beads. The flow of liquid through the liquid flow passage is regulated by a control valve which is actuated by an electronic regeneration control circuit.
Salt, typically in the form of chunks or pellets, is placed in the container. Under the control of the electronic regeneration control circuit, the control valve allows a predetermined amount of water to enter the container. Providing enough salt is present, the water and salt form a saturated salt solution, or brine, which is the regenerant for the resin bed. Again, under the control of the electronic regeneration control circuit, the control valve is actuated to cause the brine to be withdrawn from the container and circulated through, and thereby regenerate, the resin in the tank.
The amount of salt remaining in the container is reduced each time a portion of the salt is dissolved to form a regenerant. The supply of salt will become exhausted after a number of regeneration cycles, unless additional salt is placed in the container. Such that the salt supply will not become exhausted, it is desirable to provide some type of alarm to indicate that the salt supply is close to being exhausted. Such an alarm may be formed as a part of the electronic regeneration control circuit.
While such systems have been provided in the past, various shortcomings in the design and operation of such systems have been observed. For instance, U.S. Pat. No. 4,987,409 --Jackson, entitled: LEVEL SENSOR AND ALARM is directed towards a system wherein a sensor, in the form of a position responsive switch, is placed in a salt brine tank. As set forth in the Jackson patent, the sensor 52 includes a mercury switch 68, the contacts of which are open as long as the sensor is resting on salt. The sensor is weighted such that the contacts close when the salt level is reduced to a level such that the sensor 52 floats on the liquid in the tank. The level sensor disclosed in the Jackson patent, and others which place an electronically conductive sensor in the brine tank, are subject to the very corrosive atmosphere which exists within the brine tank.
It is well known that a salt-brine laden atmosphere is very corrosive by nature. Placed in such an atmosphere, any electrical device, which necessarily includes metal conductors, is subject to corrosion which ultimately will result in the failure of the device. Further, mercury being considered a hazardous material, it is undesirable to locate a switch, such as shown in the Jackson patent, in a brine tank. Should mercury escape from the switch, it will come in contact with water potentially to be consumed by humans.